Liposomal formulation of mirfentanil hydrochloride

Mirfentanil hydrochloride, a novel CNS analgesic with a short duration of action, was successfully encapsulated in liposomes having a variety of compositions. The lipid composition of the formulation was varied to optimize the stabilization of liposomes and the encapsulation of solutes. Retention of mirfentanil hydrochloride was evaluated by storing loaded liposomes at several temperatures, and also after the physical stressing of formulations. High efficiency of drug encapsulation was observed in liposomes prepared using dipalmitoyl-L-alpha-phosphatidylcholine (DPPC) and the ternary mixture of dimyristoyl-L-alpha-phosphatidylcholine, cholesterol, and dicetyl phosphate (DMPC/CHOL/DCP), both with and without the further incorporation of monosialoganglioside (GM1). Only 35% of encapsulated drug was lost when the formulations containing GM1 were incubated with human plasma over a 24 hour period, suggesting that liposomal formulations containing GM1 could be used to control drug release in vivo.